VMware ESXi and vSphere Cluster Management

NFS Components in VMware ESXi

Learn how NFS servers, exports, VMkernel networking, the ESXi NFS client, and NFS datastores work together in vSphere.

What Is NFS?

Network File System (NFS) is a network file-sharing protocol. It allows a client to access files and directories stored on another system over a network as though they were shared storage.

In a vSphere environment, an ESXi host uses NFS to access file-based storage provided by a NAS appliance or another NFS-capable server. NAS means Network Attached Storage: a storage system that commonly provides file shares through protocols such as NFS.

NFS communication uses standard TCP/IP networking. The ESXi host sends storage requests through its VMkernel networking, across the IP network, to the NFS storage system.

NFS Architecture in vSphere

The three central components are the NFS server or device, the built-in ESXi NFS client, and the NFS datastore visible in vSphere.

An NFS server or NAS owns the physical storage capacity and exports a directory.
The ESXi host uses its integrated NFS client to connect to that export.
The ESXi host presents the mounted export as an NFS datastore.
Virtual machines and other vSphere files use the datastore through the ESXi host.

The communication path is therefore:

ESXi host
  → VMkernel port
  → virtual switch or distributed switch
  → physical TCP/IP network
  → NFS server or NAS
  → exported directory
  → NFS datastore mounted by ESXi

The datastore object shown in vSphere is not a locally formatted block volume. It is the ESXi representation of a server-side directory that has been exported and mounted through NFS.

NFS Components and Responsibilities

Component	Location	Primary responsibility	Examples of relevant configuration
NFS server or NAS	Storage system	Owns storage capacity and provides NFS services	Server address, NFS service, storage pools, export policies
NFS export	On the NFS server	Shares a directory with authorized clients	Export path, allowed ESXi addresses or subnets, access options
ESXi built-in NFS client	In each ESXi host	Connects to an export, mounts it, and performs file operations	NFS server address, export path, NFS version supported by the release
VMkernel port	ESXi networking	Provides the host interface used for NFS storage traffic	IP address, subnet, VLAN, routing, network binding
NFS datastore	vSphere inventory and ESXi host	Represents the mounted NFS export as shared storage	Datastore name, mounted hosts, available capacity

The NFS Server or NFS Device

The NFS server is the NAS appliance or server that exports directories over the network. It owns and presents the underlying storage capacity. The physical disks, storage pools, quotas, snapshots, and other storage features are managed on that system rather than inside the ESXi datastore object.

An NFS export is a directory on the NFS server that is shared with authorized clients. For an ESXi host to mount an export, the host needs two important pieces of information:

The NFS server address, such as an IP address or a resolvable hostname.
The exact exported directory path, such as /exports/vmware-prod.

The server's export rules determine which ESXi host addresses or networks may access the directory. Creating the directory and configuring its export permissions are server-side tasks performed on the NAS or NFS server.

The Built-in ESXi NFS Client

Every ESXi host that uses NFS relies on its integrated NFS client. The client connects to the NFS server, mounts an authorized export, and performs file operations against the remote directory.

The client does not provide the physical capacity. Instead, it provides the ESXi capability required to use capacity presented by the NFS server. Each ESXi host that needs access must have both:

Network connectivity from an appropriate VMkernel interface to the NFS server.
Authorization from the NFS server's export policy.

In a cluster, multiple ESXi hosts can mount the same export when the hosts are configured and authorized appropriately. The export policy must account for every host that requires access.

NFS Datastores

An NFS datastore is an ESXi-mounted NFS server export used as shared storage. vSphere displays it as a datastore, but the underlying resource remains a directory managed by the NFS server.

Common content on an NFS datastore includes:

Virtual machine configuration files.
Virtual machine disk files.
Virtual machine templates.
ISO images used for installation or maintenance.
Snapshots and other vSphere-related files, where supported and appropriate.

Multiple ESXi hosts can mount the same export. This is a major shared-storage characteristic: the hosts can access common virtual machine files without each host having a separate local copy of the datastore.

VMkernel Networking for NFS

ESXi accesses NFS storage through VMkernel network adapters. A VMkernel port is an ESXi networking interface used for host services, including storage traffic. It is separate from the network interface presented to a virtual machine guest.

The VMkernel port connects through an ESXi virtual switch or a distributed virtual switch. The switch connects the VMkernel interface to physical uplinks and, ultimately, to the storage network.

Basic Network Requirements

The VMkernel adapter must have appropriate IP addressing.
The VMkernel interface must be connected to the correct virtual switch or distributed-switch port group.
The storage VLAN must be configured consistently across the required physical and virtual switches.
Routing must allow communication between the VMkernel interface and the NFS server when they are on different IP networks.
Physical uplinks, switches, firewalls, and other network controls must permit the required NFS traffic.
The NFS server must be reachable from the intended ESXi VMkernel address.

Storage traffic uses the VMkernel storage network, not the virtual machine guest network. Management traffic may use another VMkernel interface or network path. Separating these paths can make the design easier to operate and troubleshoot, although the exact network design depends on the environment.

NFS Storage Communication Path

Step	Component	Function	Key dependency
1	ESXi host	Requests access to the NFS datastore for host and virtual machine operations	The host must have an operational NFS client and datastore configuration
2	VMkernel adapter	Provides the source interface for NFS storage traffic	Correct IP configuration and reachability
3	Virtual switch and physical network	Carries traffic between ESXi and the storage system	Correct port group, VLAN, uplinks, routing, and firewall rules
4	NFS server	Receives NFS requests and provides access to the exported directory	NFS service availability and export authorization
5	Export mounted as datastore	Exposes the remote directory to vSphere as shared storage	Correct server address, export path, permissions, and mount status

NFS Access Controls

NFS server export rules determine which client IP addresses or networks may access a shared directory. An ESXi host outside the authorized range may be unable to mount the export even when the server is reachable over the network.

Before mounting an export, grant permission to the correct ESXi host addresses or storage-network subnet. In a cluster, include every ESXi host that must use the datastore. A configuration is complete only when these three areas agree:

Authorization: the NFS export permits the required ESXi addresses or subnet.
Reachability: the VMkernel storage interface can communicate with the NFS server.
Mounting: the ESXi host uses the correct server address and export path.

Access-control details and available options depend on the NFS server platform and the NFS version in use. Consult the NAS or server configuration for its supported export permissions, identity behavior, and security options.

For more detail about server-side permissions, see Access Controls in NFS.

Basic NFS Datastore Configuration Information

Whether configuration is performed in the vSphere interface or through supported ESXi tools, collect these values first:

NFS server IP address or resolvable hostname.
Exact NFS export path.
Desired datastore name in vSphere.
VMkernel adapter IP address and storage-network assignment.
Virtual switch or distributed-switch port group assignment.
Storage VLAN, routing, and firewall reachability.
NFS export permissions for the required ESXi host IP addresses or subnets.

Optional ESXi CLI examples for inspecting or adding NFS storage are shown below. Use syntax and supported options appropriate to the installed ESXi release and NFS version.

esxcli storage nfs add -H <nfs-server> -s <export-path> -v <datastore-name>
esxcli storage nfs list
esxcli storage filesystem list

The first command uses an NFS server address, an export path, and a datastore name. The listing commands help verify mounted NFS filesystems and storage visibility. Server-side export creation and permission configuration are performed on the NAS or NFS server, not by ESXi.

Practical Example: Basic NFS Datastore Layout

Suppose a NAS exports /exports/vmware-prod. Two ESXi hosts each have a VMkernel storage interface on the same reachable storage network.

The NAS export policy permits the VMkernel IP address of both ESXi hosts.
Each host can reach the NAS through its virtual switch, VLAN, physical uplink, and IP network.
Each host's built-in NFS client mounts the same server export.
vSphere presents the mounted export as one shared NFS datastore.
The datastore stores virtual machine files and installation ISO images.

The two ESXi hosts share access to the export, but the physical capacity and server-side directory remain managed by the NAS.

Practical Example: Export Authorization

An NFS server may allow access only from a particular storage-network subnet. If an ESXi host uses a VMkernel address outside that subnet, the host may be unable to mount the export. Updating the export rule to include the correct host address or authorized subnet resolves the authorization part of the problem, provided network connectivity is also available.

Practical Example: Separating Storage Traffic

An ESXi host can use one VMkernel adapter for NFS storage and a separate network path for management traffic. The NFS VMkernel adapter must be connected through the correct virtual switch or distributed switch, VLAN, and physical uplink to reach the NAS. The separation does not remove the need for correct routing and export authorization.

Troubleshooting NFS Components

The NFS Datastore Cannot Be Mounted

Likely causes include an incorrect or unresolvable NFS server address, an export path that does not exactly match the server-side path, missing VMkernel connectivity, an export policy that does not authorize the host, or a VLAN, routing, firewall, or physical-uplink problem.

Verify the NFS server address and exact exported directory path.
Verify the VMkernel IP configuration and network path to the NFS server.
Review the NFS server's export permissions.
Confirm that the intended VMkernel port is connected to the correct storage network.

One ESXi Host Works but Another Does Not

Compare the hosts rather than assuming the datastore itself is unavailable. The inaccessible host may lack a valid VMkernel storage path, may use a different VLAN, route, or DNS configuration, or may not be included in the NFS export rule. It may also simply not have the datastore mounted.

Compare VMkernel networking and datastore mount status across the hosts.
Confirm that the NFS server allows every required ESXi host address.
Validate the server address and export path on the affected host.

The Datastore Is Mounted but Files Are Missing

The host may have mounted a different export than intended, or the NFS server export may map to a different directory. Server-side permissions or access rules may also limit visibility.

Confirm the mounted export path.
Inspect the server-side directory associated with the export.
Review NFS server permissions and export configuration.

Exam-Relevant Notes

NFS is a file-sharing protocol that uses TCP/IP networking.
The NFS server or NAS owns the underlying storage and exports directories.
The ESXi NFS client mounts the remote export and performs file operations.
An NFS datastore represents a mounted server-side export, not a locally formatted block volume.
NFS storage traffic uses ESXi VMkernel networking rather than virtual machine guest networking.
Every ESXi host requiring access needs both network reachability and authorization in the NFS export policy.
Multiple ESXi hosts can mount the same export when configuration and authorization are correct.

For related storage foundations, review Datastore in Virtual SAN and compare the roles of different datastore technologies. The broader VMware ESXi Online Course provides additional ESXi administration context.